Monoclonal antibodies to human high molecular weight-melanoma associated antigen

ABSTRACT

The present invention provides monoclonal antibodies that react against high molecular weight melanoma-associated antigen. These antibodies may be used for diagnostic and/or therapeutic purposes.

This application is a Continuation of pending U.S. patent applicationSer. No. 10/307,757, filed Dec. 2, 2002, which claims priority to U.S.provisional application No. 60/334,368, filed on Nov. 30, 2001, thedisclosure of which is incorporated herein by reference.

FIELD OF THE INVENTION

This invention relates generally to the field of antibodies and moreparticularly to monoclonal antibodies to the human high molecularweight-melanoma associated antigen.

BACKGROUND OF THE INVENTION

Melanomas are tumors of the skin, less frequently of mucous membranes,some of which are benign. Malignant melanomas are carcinomas ofneuroectodermal origin generally derived from melanocytes(pigment-producing cells), sometimes from mucous membranes, the chorioidcoat or the meninges. There are several types of malignant melanomawhich differ in localization, way of spreading and production ofmetastases.

Conventional treatment of melanoma includes surgery, radiation orchemotherapy, and the application of biological response modifiers.However, these methods have proven to be insufficient to prevent tumorrecurrence, and are complicated by significant side effects. Therefore,it is desirable to develop therapeutic approaches which overcome thesedrawbacks and can replace or be used in combination with conventionaltreatment.

Since the immune system seems to be heavily involved in the pathogenesisof this disease, attention has now turned to active immunotherapy, forexample based on specific antigens. In melanoma, an example of suitabletargets for the production of antibodies and the development ofimmunotherapeutic approaches are the melanoma associated antigens (MAA),a number of which have been identified and characterized by theirmolecular weight, for example high molecular weight-melanoma associatedantigen (HMW-MAA) with a molecular weight of >1,000,000.

Although not immunogenic in patients with melanoma, HMW-MAA is expressedin at least 80% of melanoma lesions; has a restricted tissuedistribution; patients with melanoma possess an immune repertoire thatrecognizes this antigen and is considered to play a role in themetastatic potential of melanoma.

SUMMARY OF THE INVENTION

The invention provides monoclonal antibodies and/or antibody fragmentsto human high molecular weight melanoma associated antigens. Theantibodies or fragments thereof may be used for diagnosis of melanoma orfor therapeutic purposes. The invention also provides hybridoma celllines which produce the monoclonal antibodies specific for the HMW-MAA.

DESCRIPTION OF THE INVENTION

This invention provides monoclonal antibodies or antibody fragments tomelanoma associated antigens. The antibodies or fragments thereof may beused for diagnosis of melanoma and/or for therapeutic purposes.

The term “antibody fragments” as used herein for purposes of thespecification means a portion or fragment of the intact antibodymolecule wherein the fragment retains antigen binding function. Examplesof such fragments include F(ab′)₂, Fab′, Fab, Fv, scFv, Fd′ and Fdfragments. Method for producing various fragments are well known tothose skilled in the art.

For preparation of the antibodies, the High Molecular weight-MelanomaAssociated Antigen (HMW-MAA) bearing human melanoma cells can be used.The cells can be incubated with IFN-γ. Animals may be immunized withwhole cells, cell lysates or purified HMW-MAA. Animals suitable forimmunization include mice, rats, rabbits and goats.

Immunogenic conjugates of HMW-MAA can be prepared by standard methodsknown in the art such as by adsorption of the immunizing antigen to thecarrier or by coupling using periodate, glutaraldehyde, carbodiimidese.g. N, N′-o-phenylene-dimaleimide,N-(-m-maleimidobenzoyloxy)-succinimide,N-(3→2′-pyridyldithio!-propionoxy)-succinimide, N-ethyl-N′-(3-dimethylaminopropyl)-carbodiimide or the like. A commonly used conjugate isinvolves conjugating the antigen to keyhole limpet haemocyanin (KLH)with glutaraldehyde.

The immunogen may be mixed with adjuvants, i.e. agents which willfurther increase the immune response, for the immunization procedure.Examples of suitable adjuvants are Freund's complete adjuvant (emulsionof mineral oil, water, and mycobacterial extracts), Freund's incompleteadjuvant (emulsion of water and oil only), mineral gels, e.g. aluminumhydroxide gels, surface active substances such as lysolecithin,polyanions, peptides, BCG (Bacillus Calmette-Guerin), etc.

Immunization can be carried out by standard routes of immunizationincluding intradermal, subcutaneous, intramuscular, intraperitoneal,intravascular and intracranial injections. Since high antibody titersare desired, a series of injections is commonly given. The immunizationis for example performed by injecting the antigen two, three, four ormore times parenterally, e.g. intraperitoneally and/or subcutaneously,in regular or irregular intervals of a few days, e.g. three to sevendays, up to several months, for example four weeks.

After immunization, the antibody producing cells may be recovered fromthe immunized animal. The antibody producing cells may be spleen cellsor lymph node derived B cells. Antibody-producing cells recovered fromthe immunized mice, preferably lymphoid cells such as spleenlymphocytes, taken for example one to five days after the finalinjection, are fused with the cells of a continuous cell line, i.e. acontinuously replicating cell clone which confers this replicationability to the hybrid cells resulting from the fusion. An example forsuch a cell line is a tumor cell line (myeloma) which does not itselfactually produce immunoglobulins or fragments thereof but has thepotential to produce and secrete large amounts of antibody, and whichcarries a genetic marker so that the hybrid cells can be selectedagainst non-fused parent cells. Several suitable myeloma cell lines areknown in the art. Preferred are myeloma cell lines lacking the enzymehypoxanthine guanine phosphoribosyl transferase (HGPRT) or the enzymethymidine kinase (TK), which therefore do not survive in a selectiveculture medium containing hypoxanthine, aminopterin and thymidine (HATmedium). Particularly preferred are myeloma cells and derived cell linesthat do not survive in HAT medium and do not secrete immunoglubulins orfragments thereof, such as the cell lines P3×63Ag8.653 or Sp2/0-Ag14.

The fusion is performed in the presence of a fusion promoter, forexample Sendai virus or other paramyxo viruses, optionally inUV-inactivated form, or chemical fusogens such as calcium ions,surface-active lipids, e.g. lysolecithin, or polyethylene glycol (PEG),or by electrofusion. Preferentially, the myeloma cells are fused with athree-to twentyfold excess of spleen cells from immunized mammals in asolution containing about 30% to about 60% of polyethylene glycol of amolecular weight between 1000 and 4000.

After the fusion, the cells are resuspended and cultivated in aselective medium chosen depending on the genetic selection marker, forexample HAT medium. In this medium, only hybridoma cells will survive,because they combine the ability to grow and replicate in vitroinherited from the parent myeloma cells and the missing HGPRT or TKgenes essential for the survival in HAT medium inherited from theantibody-producing spleen cells of the immunized mammals.

Suitable culture media for the expansion of hybridoma cells are thestandard culture media, such as Dulbecco's Modified Eagle Medium (DMEM),minimum essential medium, RPMI 1640 and the like, optionally replenishedby a mammalian serum, e.g. 5% to 15% fetal calf serum. The culture mediaare supplemented with selective medium in order to prevent myeloma cellsfrom overgrowing the hybridoma cells. The supernatant of the hybridomacells can be screened for the monoclonal antibodies. For example,hybridomas may be selected from the fused cells by radioimmunoassay,enzyme-labeled immunoassay (ELISA), fluorescence labeled immunoassays orthe like using HMW-MAA.

Positive hybridoma cells are cloned, e.g. by limiting dilution or insoft agar, preferentially twice or more. Optionally, hybridoma cells arepassaged through animals, e.g. mice, by intraperitoneal injection andharvesting of ascites, which stabilizes hybridomas and improves growthcharacteristics. The cloned cell lines may be frozen in a conventionalmanner. In a preferred embodiment, hybridomas producing the monoclonalantibodies TP109 and VF20-VT1.7 were produced.

Also provided in this invention are the hybridoma cell lines whichsecrete the monoclonal antibodies of the present invention. Inparticular, the invention provides hybridoma cell lines which arehybrids of myeloma cells and B lymphocytes of a mouse immunized with amonoclonal antibody directed against high molecular weight-melanomaassociated antigen. Preferentially, these cell lines are hybrids ofmouse myeloma cells and B lymphocytes of a mouse, for example a Balb/cmouse, immunized with melanoma cells. Especially preferred is thehybridoma cell line which secretes monoclonal antibody TP109 and thehybridoma cell line which secretes the monoclonal antibodies VF2O-VT1.7.The hybridoma cell lines of the invention may be kept in deep-frozencultures and reactivated by thawing and optionally re-cloning.

The invention also provides pharmaceutical compositions comprising amonoclonal antibody and/or a fragment thereof according to theinvention. The pharmaceutical compositions comprise, for example, themonoclonal antibodies and/or fragments thereof in a therapeuticallyeffective amount together or in admixture with a pharmaceuticallyacceptable carrier.

The antibodies of the present invention may be used for diagnostic andtherapeutic purposes. The antibodies of the present invention can beused for qualitative or quantitative detection of melanoma and othertumor cells. The detection is carried out by standard immunologicalmethods well known in the art. The antibodies obtained according to thepresent invention can thereby be used as such or may be labeled orconjugated (such as to toxins). Thus, the monoclonal antibodies can beused for tumor targeting

The antibodies according to the present invention can also be used forthe progress of a treatment regimen or as a prognostic indicator. Aftertreatment of a melanoma patient by conventional treatments such asradiation etc., the antibodies of the present invention can be used todetermine the presence of the antigen in the body fluids. The level ofthe antigen may also be determined following treatment.

The present invention also provides a process for the diagnosis ortherapy of tumors and especially of melanomas, wherein there isadministered one or a mixture of several antibodies according to thepresent invention, optionally together with conventional pharmaceuticalcarrier, adjuvant, filling and additive materials.

The antibodies of the present invention have the characteristics asdescribed in the examples given below. The following examples arepresented for illustrative purposes and are not intended to berestrictive.

EXAMPLE 1

mAb TP109

For this antibody, a BALB/c mouse was immunized four times at 2 weekintervals with intramuscular injections of 3×10⁶ cultured human melanomacells Colo38 which had been incubated with IFN-γ (final concentration1000 U/ml for 48 hours at 37° C. Spleen cells were obtained from theimmunized mouse and fused with murine myeloma cells Ag8.X.653.Hybridizations and subcloning were performed according to standardprocedures. The supernatant from the hybridomas was tested for reactionwith melanoma cells Colo 38. A positive reacting hybridoma, labeledherein as TP109 was identified. The supernatant of this hybridomareacted with Colo 38 cultured human melanoma cells but not with culturedhuman B lymphoid cells LG2 as determined by ELISA.

When tested with a panel of cultured human melanoma cells in a bindingassay, mAb TP109 reacted with HMW-MAA bearing human melanoma cells butdid not react with cultured human B lymphoid cells and with culturedhuman carcinoma cells. The latter two types of cells do not expressHMW-MAA. Furthermore, mAb TP109 immunoprecipitated from radiolabeledcultured human melanoma cells Colo 38 components with the characteristicelectrohpretic profile of HMW-MAA when analyzed by SDS-PAGE.

EXAMPLE 2

mAb VF20-VT1.7 and VT68.2

For these antibodies a BALB/c mouse was immunized five times at 3 weekintervals with intramuscular injections of approximately 200 μl of abead suspension. The bead suspension had been preincubated with a NP40lysate of 1×10⁷ cultured human melanoma Colo 38 cells. Spleen cells wereobtained from the immunized mouse and fused with murine myeloma cellsAg8.X.653. Hybridizations and subcloning were performed according tostandard procedures. The supernatants from the hybridomas were testedfor reaction with melanoma cells Colo 38. The hybridomas, VF20-VT1.7 andVT68.2 were found to react with cultured human melanoma cells Colo 38,but not with cultured human B lymphoid cells LG2 in a binding assay.

When tested with a panel of cultured human melanoma cells in a bindingassay, mAbs VF20-VT1.7 and VT68.2 reacted with HMW-MAA bearing humanmelanoma cells but did not react with cultured human B lymphoid cellsand with cultured human carcinoma cells. Furthermore, mAb VF20-VT1.7 andVT68.2 immunoprecipitated from radiolabeled cultured human melanomacells Colo 38 components with the characteristic electrohpretic profileof HMW-MAA when analyzed by SDS-PAGE.

It will recognized by those skilled in the art that routinemodifications to the methods and compositions presented here arepossible. Such modifications are intended to be within the scope of thisinvention.

1. A monoclonal antibody which specifically binds to human highmolecular weight melanoma associated antigen (HMW-MAA) bearing humanmelanoma cells but not to human B lymphoid cells, wherein the monoclonalantibody is designated as TP109.
 2. (canceled)
 3. A monoclonal antibody,which specifically binds to human high molecular weight melanomaassociated antigen (HMW-MAA) bearing human melanoma cells but not tohuman B lymphoid cells, wherein the monoclonal antibody is designated asVF20-VT1.7.
 4. A pharmaceutical composition comprising the monoclonalantibody of claim 1 or
 3. 5. The pharmaceutical composition of claim 4,wherein the monoclonal antibody is TP109.
 6. The pharmaceuticalcomposition of claim 4, wherein the monoclonal antibody is VF20-VT1.7.